Along with the rapid distribution of information-related equipment such as personal computers in recent years, the development of batteries that are utilized as electric power sources thereof has been advanced. Furthermore, the development of batteries for electric vehicles or hybrid vehicles is in progress in the automobile industry as well. Currently, among various batteries, lithium batteries are attracting attention because of their high energy densities.
With regard to the lithium batteries that are currently available in the market, since liquid electrolytes including flammable organic solvents are used, installation of safety devices that suppress temperature increase at the time of short circuits is needed. Meanwhile, since all solid lithium batteries that have been produced into all solid state batteries by converting the liquid electrolyte to a solid electrolyte layer do not use flammable organic solvents in the batteries, it is contemplated that simplification of safety devices can be promoted, and the all solid lithium batteries are excellent in view of the production cost and productivity.
In the field of an all solid lithium battery, there has been an attempt to enhance battery performance by focusing on an interface between an active material and a solid electrolyte material. For example, Patent Literate 1 discloses an all solid lithium battery containing a lithium ion conductive solid electrolyte mainly composed of a sulfide and a cathode active material the surface of which is coated with lithium ion conductive oxide. Furthermore, as an example of the lithium ion conductive oxide, LiNbO3 has been described.